1. Field of the Invention
This invention relates to an edge detector, preferably for use on line width measuring apparatus for LSI patterns, encoder and others.
2. Related Background Art
Prior art detectors typically intended for this kind of measurement include a device for detecting an edge by applying a laser beam spot to a tested pattern and detecting scattered light from the pattern edge. Then, that of using an electron beam includes an electron beam device for detecting a tested pattern edge by applying a heat emission electron from a cathode or a field emission electron to a tested matter in concentration and detecting a secondary electron emitted from the tested matter.
However, in the case of prior art devices using laser beams, resolution cannot be minimized inasmuch as a beam spot size cannot be reduced any further than a limit, and satisfactory precision is not obtainable for detection of VLSI pattern edges of the semiconductor wafer further reduced down in structure, recently. Then, while attaining 10 nanometers of resolution anyhow, the device using electron beams is also not yet satisfactory for detection of VLSI pattern edges. Furthermore a vacuum system is required. Therefore, the device gets unavoidably large in size and working efficiency deteriorates, in addition.